The move saw the hourly rate of workers with at least two years’ experience rise from £24.54 to £41.23.

But it failed to stem the rise in vacancies, which stood at 156 this month against 80 last November.

Now the council has decided the salary increase will remain in place.

Yvette Waide, assistant director for the council’s people directorate, said: “There is a national shortage of qualified and experienced social workers and the market is already very competitive.”

She said social workers were being lost to neighbouring authorities who were paying higher salaries on top of “golden hellos” of up to £10,000.

“Demand is high from other local authorities who all want to sustain or improve performance,” she added.

“The net result is that agency workers are not being attracted to [Birmingham] city council.

“We are seeking to fill as many posts as possible within the budget limitations.

“Child protection is our highest possible priority.”

The beleaguered child protection department, rated inadequate for the past five years, was branded a “national disgrace” by the Government’s chief inspector of schools last October.

Failings by social workers and other child protection staff were highlighted in a series of serious case reviews into the death of children, including Birmingham youngsters Keanu Williams and Khyra Ishaq.

Last month the Mail revealed the department had launched a three-month campaign to recruit permanent social workers from Scotland, Ireland and London, after “exhausting” the Midland market.